fix: raise better error if field widget serialization fails

and log a warning with traceback while we're at it

src/wuttaweb/forms/base.py

@@ -1138,7 +1138,18 @@ class Form:  # pylint: disable=too-many-instance-attributes,too-many-public-meth
             field = dform[fieldname]
             if readonly:
                 kwargs["readonly"] = True
-            html = field.serialize(**kwargs)
+
+            try:
+                html = field.serialize(**kwargs)
+            except Exception as exc:
+                log.warning(
+                    "widget serialization failed for field: %s",
+                    fieldname,
+                    exc_info=True,
+                )
+                raise RuntimeError(
+                    f"widget serialization failed for field: {fieldname}"
+                ) from exc
 
         else:
             # render static text if field not in deform/schema

tests/forms/test_base.py

@@ -587,6 +587,14 @@ class TestForm(WebTestCase):
             html = form.render_vue_field("foo")
             self.assertIn("something is wrong", html)
 
+        class BadWidget(deform.widget.Widget):
+            def serialize(self, **kwargs):
+                raise NotImplementedError
+
+        # widget serialization error
+        dform["foo"].widget = BadWidget()
+        self.assertRaises(RuntimeError, form.render_vue_field, "foo")
+
         # add another field, but not to deform, so it should still
         # display but with no widget
         form.fields.append("zanzibar")